Fred Dekker has posted an explanation of why the Emissary Predators were cut in the comments on his FB page.

Copy and paste of what he said -

Quote

It was a mutual decision. We grew concerned that we were already making a movie that veered away from fan expectations, and when we showed it to some small, select audiences, our concerns were validated... so we removed the Emissaries AND the hybrids in favor of a traditional "hunt" finale, which -- in my opinion -- squandered the notion that the Predators have a larger, unseen civilization and other concerns besides sports hunting -- like, for instance, saving their civilization from extinction. It was decided that this, plus the humor in the film, was too much for the Predator fan base to swallow... and sadly, the box office and critical reception proved we were right. We should have made a cheaper, more predictable movie, and not tried to do something new.

It was a mutual decision. We grew concerned that we were already making a movie that veered away from fan expectations, and when we showed it to some small, select audiences, our concerns were validated... so we removed the Emissaries AND the hybrids in favor of a traditional "hunt" finale, which -- in my opinion -- squandered the notion that the Predators have a larger, unseen civilization and other concerns besides sports hunting -- like, for instance, saving their civilization from extinction. It was decided that this, plus the humor in the film, was too much for the Predator fan base to swallow... and sadly, the box office and critical reception proved we were right. We should have made a cheaper, more predictable movie, and not tried to do something new.

But what do I know? I was just the co-writer.

So the problem was not the quality in scripting, casting, direction and execution, it was that they tried something new and the fans (and critics?) wanted predictable.

Speaking of comics, I think they can get away with "stylizing" Predator designs in ways that live action can't. Like there are a lot of Predator comics that heavily change up how Predator faces look ('Predator: Homeworld' comes to mind) and I can dig it on a "creative interpretation" level even if it's not my cup of tea, but translating some of those designs to live-action would be a disaster. I think a bunch of these concept drawings illustrate that pretty well.

Gillis mentioned in the podcast that having to design around putting a human head under the mask really changes how the head can look. A lot of fan art and comic stuff couldn't be done as suits that required an actor's eyes to be used in the mask, for example. Really interesting stuff.

It was a mutual decision. We grew concerned that we were already making a movie that veered away from fan expectations, and when we showed it to some small, select audiences, our concerns were validated... so we removed the Emissaries AND the hybrids in favor of a traditional "hunt" finale, which -- in my opinion -- squandered the notion that the Predators have a larger, unseen civilization and other concerns besides sports hunting -- like, for instance, saving their civilization from extinction. It was decided that this, plus the humor in the film, was too much for the Predator fan base to swallow... and sadly, the box office and critical reception proved we were right. We should have made a cheaper, more predictable movie, and not tried to do something new.

But what do I know? I was just the co-writer.

So the problem was not the quality in scripting, casting, direction and execution, it was that they tried something new and the fans (and critics?) wanted predictable.

It's the fine line (not that subtle though) between adding to a franchise and just kicking it in the nuts by doing the complete opposite of what fans love.

In a way, The Last Jedi toyed with people's expectations too, but it managed to keep it all in character (if you're willing to accept it not living up to your personal fanboy dreams) rather than just make it about something completely different.

The Predator is a nice film, just a very poorly thought through sequel. Whoever pushed this through Fox should ask themselves if they get what the franchise is about.

I think most would agree from the get go that the script didn't made much sense overall. What happened next is a mix between Shane wanting some of his vision to be present in the movie and studio interferences.

Yeah, it seemed like a lost cause from the start. The version we got or the original, it would have made little difference overall.

I think it would be much, much worse if the studio didn't intervene. It really looks like Fox backtracked this movie from being maybe a franchise killer to a not great, but still watchable (imo) Predator movie.